Astronomers from the University of Minnesota at Duluth and the North Carolina Museum of Natural Sciences have discovered a new class of ring-shaped galaxies. The found galaxy, called PGC 1000714, has an elliptical core not with one, but with two outer rings. At the moment, this is the only galaxy of this type that scientists have encountered.
Most galaxies are disk-shaped or spiral-shaped, but sometimes very unique specimens are found. For example, the same lenticular galaxies, which are a kind of middle ground between spiral and disk-shaped galaxies, or irregular galaxies with an indistinct structure, almost amorphous. There are galaxies with ultra-low density star clusters.
The "regular" ring-shaped galaxy known as the "Hog's Object"
Ring-shaped galaxies also fall under the classification of unusual galaxies. These incredibly beautiful space objects have a well-defined elliptical core surrounded by a single ring of stars (unconnected). One of the most famous galaxies of this type is the Hoag Object (pictured above), discovered in 1950 and named after the famous astronomer and discoverer Arthur Hoag. Ring-shaped galaxies, which are often called "Hoag objects", are very rare in the Universe - they account for less than 0.1 percent of all galaxies we observe - therefore, the discovery of another representative of this rare type, and even such an unusual one, greatly delighted astronomers …
According to an article published in the Monthly Notices of the Royal Astronomical Society, we may officially add another newcomer to the list of these rare galaxies, but the newly discovered ring galaxy deserves a new subclass. The fact is that its elliptical core is surrounded by two distinct and independent rings at once.
Object PGC 1000714, or the Burkin galaxy (named after the astronomer Burkin Mutlu-Pakdil, who discovered it), is located about 359 million light years away. Its unusual structure allows astronomers to better understand the question of how galaxies form and develop.
On the left is a pseudo-color image of the galaxy PGC 1000714. On the right is a two-color composite image showing the outer ring (in blue) and a more blurred inner ring (in light green)
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By analyzing images of the galaxy in different light spectra, the researchers found a blue (about 0.13 billion years old) outer ring surrounding a red (about 5.5 billion years old) central elliptical core. However, unexpectedly for themselves, scientists also discovered a second, inner ring surrounding the galactic center.
“We have seen blue-ring galaxies around a central red body before. The most famous such object is the "Hoog object". However, the uniqueness of the newly discovered galaxy lies in the fact that it has an additional second, older and thinner red ring,”- said Patrick Trotardt, astrophysicist at the North Carolina Museum of Natural Sciences and co-author of the study.
While astronomers are not ready to give a solid answer to the question of how ring-shaped galaxies are formed, however, most likely, the outer boundaries of such galaxies are formed as a result of collisions of gases.
“The different colors of the inner and outer rings suggest that this galaxy experienced two different formation periods,” says Mutlu-Pakdil.
Scientists believe it will be nearly impossible to figure out how the rings of this particular galaxy were formed.
“Whenever we find a unique or strange object to study, each time this event forces us to take a fresh look at our current theories about how the universe works. As a rule, each time it turns out that we have a lot more to learn,”concludes Trotardt.
NIKOLAY KHIZHNYAK